Contact form uses a set of alias (the @Aliases variable) to allow email to be sent. Each alias
has two parts: a public name, and a private email address. The address is never shown on the
contact form page or in the page source.

$Aliases = [
'contact_administrator_name', 'contact_administrator_email',
#### The following aliases are commented out examples, remove the leading # sign to use them
## A simple example of mail sent to John Smith
#'John Smith','john@yoursite.tld',
## Here both the name and the email are translated.
## Translations can be edited in the translations section.
#'contact_customer_support_name','contact_customer_support_email',
## Just the name is translated
#'contact_postmaster_name','postmaster@yoursite.tld',
## A mailing list with multiple addresses separated by commas
#'two people','webmaster@yoursite.tld,postmaster@yoursite.tld',
];

The lines that start with # are commented out. In this configuration the form will
send email only to the web server administrator (as defined in the web server configuration).
It is almost certain that you want to change this.